1. Field of the Invention
The present invention relates to a printed board in which a connector pad consisting of a conductor pattern is formed, and more particularly, to a printed board suitable for having a LSI surface-mounted thereto.
2. Description of the Related Art
It is desired that printed boards for LSI package and the like have high-speed transmission performance. Currently, frequency band, which meets a condition that S parameter is in the range from −10 to −20 dB, is about 5 GHz. Obviously, it is expected that there will be a growing demand for higher transmission performance than before. Various ideas have been proposed to realize high-speed transmission (see Japanese Utility Model Application Publication No. 6-13181, Japanese Patent Application Publication No. 61-158198, and Japanese Patent Application Publication No. 2004-39732). However, technological development to realize still faster transmission is desired.
Printed boards have a problem that the transfer characteristic such as S parameter is hard to improve because the shape of the pad on the printed board is larger than that of the signal transmission line.
To address this problem, there has been proposed a technique of forming a pad with small circumference (Japanese Utility Model Application Publication No. 6-13181 for example). However, because the circumference of a pad is important in relation to the resistance to a vibration or thermal stress applied by a LSI connected to the pad, if the circumference of a pad is made small, there arises another problem that the pad cannot resist to vibrations or heat so that it easily peels off the printed board.